How to play

Two Sudoku techniques for beginners

Classic Sudoku asks you to place digits 1–9 exactly once in every row, column, and 3 × 3 box. Printed givens stay fixed; every move below comes from those rules.

Technique 01

Naked single

In row 1, the only digit missing is 4. After checking the column and box, cell r1c3 has just one legal candidate: 4.

Before · r1c3 is empty

After · place 4

Technique 02

Hidden single

In row 2, digit 6 can go in only one cell: r2c1. That cell could hold other candidates, so the single is hidden in the row rather than exposed in the cell.

Before · 6 has one place in row 2

After · place 6

These are the same two worked examples printed near the front of the book.

Solving checklist

The five-step checklist

Scan: look for digits missing from a row, column, and box.
List: choose an empty cell and write candidates that do not conflict with all three units.
Single cell: if that cell has one candidate left, place it as a naked single.
Single place: if a digit has only one legal place in a row, column, or box, place it as a hidden single.
Update and repeat: check what changed, update candidates, and scan again; if stuck, revisit the examples and check for an incorrect note.

Use the controls without losing your place

The Easy samples include Notes, Erase, Undo, Redo, Check, Reveal solution, and Restart. Check marks incorrect entries without changing them, and using it marks the attempt as assisted. Reveal asks for confirmation and ends that attempt; Restart begins again from the printed givens.

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